Red Bull has issued troubled engine supplier Renault with an ultimatum -- improve or be dumped.
Although the reigning world champions have emerged from the depths of a winter crisis, Dr Helmut Marko insisted Renault has a long way to go if it wants to stay under the engine cover of the team's Adrian Newey-penned cars.
Indeed, Marko has claimed the credit for much of Renault's improvement since the winter, revealing he installed a crisis team comprising Red Bull and Toro Rosso engineers at the French marque's Viry headquarters.
Now, he told Germany's Bild newspaper his patience is running out.
"If there is no noticeable improvement in two or three months, we will definitely be talking about an alternative," said Marko, who is famously close to Red Bull's team owner Dietrich Mateschitz.
Until then, he said Red Bull is working on compensating for an 80 horse power deficit through car changes -- and hoping for trouble at the front of the grands prix.
"We cannot put additional horse power in the engine ourselves," said Marko. "But we can hope for trouble between Rosberg and Hamilton and drive past them."
Mercedes' Toto Wolff admits he is aware of the potential for problems.
"We are spending quite some time discussing those things, discussing scenarios and discussing situations," he said when asked about the prospect of the driver relationship boiling over.
"It's Mercedes and it's the team that comes first, but one day it (the situation) will be rubbish," Austrian Wolff told the Mirror newspaper.
"What makes a difference is that these guys have known each other for such a long time and they have a fair relationship with each other.
"But it doesn't mean that they are not extremely competitive and that they will try to use every advantage they can," he added.